Body, generic

B003A Second Row Right Frontal Stage 2 Deployment Control

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

B003A covers stage 2 of the right rear-seat frontal airbag. The second charge allows the module to soften or strengthen inflation; for a rear bag this matters because the person behind the front seat may be an adult, a child or a child seat facing either way, a point Mercedes-Benz stressed when it introduced the S-Class rear airbag in 2020. The Mercedes filing for a bag on a sliding front backrest provides separate deployment devices so its chambers can fire one after the other. No vehicle maker documents B003A, and no bulletin with it is on record at NHTSA. A stage 2 code alone suggests the stage 2 wires or igniter rather than the whole bag. Airbag lamp on.

Likely causes

Loose or corroded connector of the airbag lead routed through the front seat backrest
Open or short only in the stage 2 pair of wires
Faulty second igniter in the right rear-seat airbag
Restraint module configured for equipment the vehicle does not have (wrong part or coding)

Symptoms

  • Airbag warning lamp on
  • Rear airbag may not adapt its inflation to the occupant
  • Safety note: do not probe the airbag circuit yourself; unplug airbag connectors only with the battery disconnected and the stated wait time observed

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€100–1,200
Time1–4 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

second row right frontal airbagsquib circuitsrs seat wiringsrs control module

Related codes

B0039B003BB0032

References: patents.google.com, repairerdrivennews.com, patents.google.com.